Though it sounds like the plot of a movie the reality is that select Army engineer, Special Forces, Navy SEALs and select Marines were once trained to employ backpack nukes.

The scientists of Los Almos Scientific Laboratory created the W54 atomic warhead in the late ‘50s.  It was one of the smallest nuclear warheads ever fielded at under 11″ diameter (270 mm), about 16″ long (400 mm) and a little over 50 pounds (23 kg).  The fuse allowed for one to select a yield from a tenth of a kiloton to a full kiloton.  The W54 was also a pretty dirty bomb.  People out to a quarter-mile away were likely to receive a deadly dose of radiation.

About 400 W54s were built. The Air Force employed some on AIM-26A Falcon AAM and the AGM-45 Walleye ASMs (to take out Russian bombers and subs, respectively). The Army employed them on the M-29 Davy Crockett, a jeep-mounted recoilless cannon tactical nuclear weapon with about a 3 km range.  That left a couple hundred to be used by SOF as the MK54 Special Atomic Demolition Munition or SADM.  The SADM was designed for a time where the US saw tactical nuclear weapons as a cheap and easy way to make up for capability.

The SADM had a combination lock covering its mechanical timer, which was EMP-proof, mounted in a shockproof case that was waterproof to 200 feet, packed onto a padded ruck.  Total weight of the SADM was a little over 160lbs.

Nuclear weapons at the small-unit level might seem pretty alien today, but early in the development of nuclear weapons their effects were underestimated and utility overestimated.  While most know what Mutually Assured Destruction is, many don’t know the nuanced history and development of US nuclear doctrine.  It evolved from one that promised massive retaliation in the event of a Soviet conventional attack to one of a flexible response.

Massive retaliation was exemplified when Secretary of Defense Forrestal wondered to National Security Council members, in reaction to the Soviets putting barrage balloons up during the Berlin Airlift, “if a reduction of Moscow and Leningrad would be a powerful enough impact to stop a war.”  While promising massive retaliation allowed the US to not have to invest in stronger conventional forces, it became apparent over time that a strategic nuclear exchange was not a solution to many contingencies.  This realization, along with a continued early underestimation of the impact of nuclear weapons, resulted in the development described above of “small” nuclear weapons applied to largely conventional targets.

Special teams chosen from Special Forces units, Navy SEALs, select Marines and Army engineers were trained in the employment of the SADM.  The Atomic Demolitions Munitions School was located at the U.S. Army Engineer Center on Ft. Belvoir, Virginia and was three-weeks long.  Army Special Forces teams attended a compressed weeklong course at Ft. Benning.

SADMs were seen at first as simply super-sized explosives.  Counter-mobility doctrine routinely uses explosives to slow the enemy’s advance, and in Europe, with the overwhelming conventional capability of the Warsaw Pact, any and every advantage to slow down communist forces was considered.  Bridges, tunnels and natural chokepoints were valid targets.  Engineers also envisioned “landscaping” on a huge scale with SADMs creating craters impossible for tanks to traverse, and blowing or creating dams to inundate avenues of approach.

US plans for the worst situations included destroying rail yards, airports, powerplants and infrastructure to keep it from assisting the Soviets.  The fact that these targets were primarily in Germany did not endear the approach with the Germans who, while allowing for the planning of the employment of SADMs, would not allow site preparation for the employment of the weapons.  Simply digging a shaft to slide a warhead into a hillside would exponentially increase the effectiveness of the munition, but for the Germans, it was seen as making the use of nuclear weapons on German soil even more likely.

SOF employment of SADMs included “landscaping” missions especially to obstruct enemy follow-on forces moving west, but SADMs were also seen as capable of taking out high-priority targets like command bunkers, ammunition depots or air defense nodes to clear the way for friendly aircraft.  The plan was to insert these select teams by parachute or helicopter.  The teams would move to the targets, set their explosives and be extracted, escape and evade, or, using prepositioned caches, conduct operations in the enemy’s rear.  SEAL employment of SADMs could include the above, but were more focused at coastal targets.

At first glance, the employment of SADMs seems innovative and creative, but the realities of employing these weapons as described were extremely unlikely.  SADMs were secured, as specific ammo depots very likely already known to the Soviets.  These were primary targets for persistent chemical munition strikes, as well as Spetsnaz operations.  In the event of war, the ability to draw these weapons from a bunker, get them to SOF units and then transport that unit behind enemy lines would have likely been extremely difficult, if not improbable.  Assuming a SADM could be successfully drawn from the bunker, transported to the team and the team was successfully inserted, hauling a 160lb pack anywhere is no easy task.  SOF would have been very vulnerable moving any distance on foot.  Some of the stories of the men that conducted training missions are fascinating as are the difficulties they overcame.

What were the factors that worked most strongly against the employment of SADMs? There are very few targets that could be attacked better with a man-employed nuclear weapon than one delivered by a plane or missile.  Secondly and thankfully, it became apparent that numerous small nuclear warheads going off would escalate to larger and larger warheads, as well as reducing the threshold for the employment of nukes.

SOF Backpack Nukes

The Atomic Demolitions Munitions School was closed in 1985, and by 1989 all SADMs were withdrawn from Europe and decommissioned.  In September of 1997, 60 minutes did an expose where Colonel Stanislav Lunev, the highest ranking GRU officer ever to defect, stated that the Soviet Union had also built small nuclear weapons that could fit in a suitcase, and were a fraction of the weight of a SADM.  Unlike the US approach, Soviet plans featured smuggling these weapons to their targets during peacetime.

I’d bet we make them smaller now, too…